We got this with fresh "uni" sea urchin and other uni products from Maruhide 丸秀 sometime ago. Finally we got around to tasting it. This is called "Uni-shutou-ruibe" うに酒盗ルイベ. I sliced it thinly while it was still frozen and served it with slices of cucumber and cold sake.
I'm quoting from my previous post: "Ruibe" is a word derived from the Ainu アイヌ, the endogenous people of my home island Hokkaido. Roughly translated, it means "thawing food". In the severe cold of Hokkaido, salmon harvested in early winter quickly froze. In its frozen state, it was sliced thinly and served semi-frozen or over hot rice where it thawed--hence thawing food.
"Shuto" 酒盗: These two letters literally mean "sake" and "stealing". The origin of this name reportedly came from the allegation that shuto is so good with sake that when people run out of sake while eating it, they are compelled to obtain more sake even if they have to steal it. There is a similar preparation called "shio-kara" 塩辛 or, as my wife calls it, "squid and guts". It is made of strips of raw squid salted and fermented with squid guts (mostly liver) which we really like and is also perfect with sake. Shuto appears to have originated and become popular in Kochi 高知 prefecture on Shikoku island 四国. This island is famous for "Katsuo" 鰹 or bonito fishing. Instead of discarding the innards (stomach and intestine), they cut them up, salt, and ferment for 1 year or more. According to what I read, the digestive enzymes present in the innards ferment and preserve the fish guts. Many variations incorporating different flavorings and using bonito flesh instead of innards as well as other fish exist but I have not tried them. "Uni shuto" appears not to contain fish innards.
We really like this. It is a cross between fresh uni and uni product called "Neri-uni*" 練りウニ. The uni flavors get concentrated. What we really noticed was the texture transition that occurred after we placed it in our mouth. It went from cold and frozen with little flavor to melt in your mouth flooding with fresh uni flavors. We really enjoyed this on slices of cucumber followed by a mouthful of cold sake but it will definitely go well with fresh white rice. "Uni-shutou-Ruibe" is not a traditional Japanese product and according to "Maruhide", this is exclusively available at "Maruhide" in Los Angeles.
*Neri-Uni: This is a more traditional preserved "uni" product. The uni is mixed with salt and alcohol. The resulting paste is packaged in a small glass jar.